Causes of high temperature weather
1, solar radiation
In summer, the direct point of the sun gradually moves from south to north, and in summer, it directly hits the Tropic of Cancer. In this process, the solar altitude angle in the northern hemisphere gradually increases, the sunshine time is longer and longer, the received solar heat is gradually increased, and the temperature is also increased. This is the basic cause of high temperature weather.
2. Atmospheric circulation
On the one hand, the specific circulation situation is easy to form high temperature weather. A typical example is the subtropical high with the title of "high temperature messenger". In midsummer, the western Pacific subtropical high controls the middle and lower reaches of the Yangtze River in China. Due to the subtropical high prevailing downward airflow, the air is strongly heated.
At the same time, local cloudy to sunny, conducive to sunshine, ground radiation is obviously warming up, easy to form high temperature and hot summer weather. In addition, weather systems such as continental warm high pressure, tropical cyclone, hot low pressure and weak cold front will also give birth to high-temperature heat waves.
On the other hand, the abnormal atmospheric circulation also has a direct impact on the formation of high temperature weather. For example, the abnormal position and intensity of subtropical high will cause the change of high temperature weather.
3. Geographical factors
The geographical location, topography, landforms and other characteristics of a place will also affect the temperature. For example, in the "history" of China, there have been three big stove cities: Nanjing, Wuhan and Chongqing.
All belong to basin topography, which is easy to store heat and not easy to dissipate heat, which is helpful to the formation of high temperature weather. For example, some areas such as the Qinghai-Tibet Plateau have never experienced high temperature weather because of their high altitude.
4. Global warming
Due to the influence of human activities and natural climate fluctuations, the global average surface temperature has been on the rise in recent 130 years. In the past few decades, the temperature in every decade is obviously warmer than that in the last decade. Under the influence of global warming, extreme high temperature events become more and more frequent.
5. Urban heat island effect
Due to the dense population and large building area of the city, the humidity and air convection of the urban surface have changed, resulting in the temperature in the city being significantly higher than that in the surrounding areas.
Nowadays, with the acceleration of urbanization, the urban heat island effect is more obvious, which contributes to the formation of high temperature weather.